If the overflow tank high-level alarm sounds while the fuel oil tanks are being topped off, the engineer should （）. ["close the static leg filling valve","close the overflow tank falling valve","reduce the fuel oil pumping rate","stop the fuel oil pumping operatio"]
在Windows 2000“资源管理器”窗口中，若文件夹图标前无任何符号，则表示该文件夹（）。 ["包含下一级文件夹，已展开","包含下一级文件夹，尚未展开","不包含下一级文件夹","无任何意义"]
下列关于PM2.5的叙述中，正确的是：（） ["大气中直径大于或等于2.5微米的颗粒物的总称","长期吸入会对人体的呼吸系统、心血管系统和神经系统产生危害","主要通过颗粒对呼吸道的粘附而干扰气体交换","主要是颗粒上携带的有毒物质通过肺泡黏附在毛细血管内壁或进入血液循环而对机体产生危害"]
After fuel tanks have been topped off, which of the listed procedures should be followed next?（） ["The pressure-vacuum relief valve should be reset","The tanks should be made seaworthy to prevent contamination","The tanks should be sounded to make sure the levels are not rising","The tanks should be marked with a bull stamp on the manifold filling valve"]
通过Windows 2000“资源管理器”的工具栏的（）按钮的组合操作，可以实现被选取对象的移动。 ["删除和粘贴","剪切和粘贴","剪切和复制","复制和粘贴"]
南部非洲有哪些主要特点？
